PROJECT SUMMARY Metastasis is the main cause of death from solid tumors including colorectal cancer (CRC). My long-term goal is to develop more selective therapeutic options to prevent or reduce the incidence of CRC metastasis by understanding how changes in de novo fatty acid synthesis contribute to metastatic disease. Fatty acid synthase (FASN), a key enzyme of de novo lipid synthesis, is significantly upregulated and activated in CRC, and its activity is associated with poor prognosis, higher risk of disease recurrence, and death. I have identified FASN as a potential target for advanced stages of disease and showed that upregulation of this enzyme is a key mechanism supporting metastasis in CRC. However, the underlying mechanisms of regulation of metastasis by FASN are not understood. The current application proposes a comprehensive research plan to study novel mechanisms of regulation of growth, survival and metastasis by FASN in CRC. Our preliminary studies show that overexpression of FASN is associated with an increase in cellular respiration, including ?- oxidation, inhibition of autophagy, and accumulation of lipid droplets. Therefore, in Aim 1, we will elucidate the role of FASN in reprogramming of metabolic pathways and lipid storage in order to maintain energy homeostasis and promote survival of cancer cells. Furthermore, our preliminary data suggest that the primary product of de novo fatty acid synthesis, palmitate, is selectively used for sphingolipid synthesis and overexpression of FASN increases the level of sphingosine-1-phosphate (S1P), a bioactive sphingolipid, known to enhance migration and invasion of cancer cells. Therefore, in Aim 2, we will test the hypothesis that FASN promotes metastasis via activation of sphingosine kinases and an increase in S1P signaling. Finally, in Aim 3, we will test the effect of FASN inhibitor on proliferation in CRC patient-derived xenografts (PDXs) as a monotherapy and in combination with an autophagy inhibitor and identify potential biomarkers associated with CRC responsiveness to FASN inhibition. I will utilize biological samples from patients, human primary cells and PDX models, which are the most advanced models for pre-clinical target and drug evaluations. These models will be used in conjunction with state-of-the-art approaches, including Stable Isotope-Resolved Metabolomics (SIRM) to evaluate the effect of FASN overexpression on cancer metabolism. The differential expression of FASN in normal versus cancer cells makes de novo lipogenesis a desirable target for therapeutic intervention. I anticipate that the proposed work will identify a subset of CRC patients who would benefit from targeted FASN inhibition and further advance our understanding of the role of FASN in CRC that would potentially lead to the development of novel therapeutic strategies to treat this disease.